This invention refers to a device for detecting sudden or slow accidental immersion of a body into a swimming pool, specifically to detect the accidental immersion of children into swimming-pools. Such an event sometimes remains unnoticed resulting in unfortunate consequences such as week-end residences, villas or clubs without guarding.
It is not actually known in practice of any kind of device or alarm for detecting this kind of accidental fall. There fore, it is important to create a means which may be capable of warning of any unnoticed sudden or slow immersion of a body into a liquid medium. In view of the above, this invention comprises a device which can be applied on any swimming pool area, thus facilitating the detection of any slow or fast immersion of a body, the volume of which may be equal to or exceed that of an infant's, that is, approximately 6 or 8 dm.sup.3.
This device generates a response based on detecting means of different physical effects such as the relative humidity variation of air impelled from within a chamber in communication with the liquid medium in the swimming pool, air thermal variations and tension variations of a semi immersed object fixed to the swimming-pool by effect of such object immersion in the swimming-pool to cause a piezo-electric or birefringent effect. The operating principle of this device is based on a response to the immersion of a body into the liquid mass in the swimming pool which causes a rise in the water level. This small level variation in a first embodiment of the invention, is separated from unwanted permanent and harmonic variations and from the surface liquid by damping the superficial waves so that the liquid may run into a small chamber in communication with the liquid mass. There, a rise in the water level as a consequence of the immersed body to be detected, causes an air flow towards a receptacle, opened to the atmospheric pressure and in which sensor devices are set of psychrometric properties of the air impelled by the rise in the liquid level in the chamber. The change and/or rate of change of air relative humidity is detected by a sensor placed in the receptacle which, in response to the humidity variation, unbalances an impedance bridge which by means of circuit components allows the generation of an electrical pulse activating an alarm. The receptacle may also have a second sensor of psychrometric properties consisting of a metal and vegetal fiber plate, whose mechanical properties are extremely sensitive to small variations of relative humidity and temperature. A variation in the sensor properties allows a variation in the intensity of a light coming from a light source which reaches a phototransistor. In a second embodiment of this invention, the chamber--in communication with the liquid medium of the swimming pool--is connected by means of a tube to a small receptacle in which a heater, such as a resistor, and a thermic sensor are placed, the receptacle being provided with an air drain. When a body falls into the swimming pool at this step, the rise in the water level of the chamber causes an air flow which is impelled towards the tube, thus changing the stationary thermal regime conditions. This temperature variation is detected by the sensor to generate a signal which, if in excess of a given value corresponding to a value given by the body volume, causes an alarm to be activated. In a third embodiment of the invention, the device is provided with a bottomless receptacle partially submerged in the liquid mass in the swimming-pool in which a floater is confined, and articulated to a wall of the confined place adjacent to the receptacle where a plate is fixed with which an arm of the floater forms a capacitor, whose capacitance variation is caused by a body immersion into the swimming-pool and it is used to generate a signal, which after being processed activates an alarm as described previously.
In a fourth embodiment, the device is furnished with a floater covering a certain area in the water and fixed with respect to a wall of the swimming pool. The floater is related to a piezo-electric crystal and when the floater is affected by a water level rise due to a body immersion, it transmits a stress on said crystal causing a signal which is then amplified and processed to activate an alarm as in previous steps. Finally, in a fifth embodiment of this invention, the floater arm, as in the previous example, is connected to the end of a non-birefringent plastic plate fixed by its opposite end to a wall of the swimming pool. The floater transmits a tension in response to a body immersion into the swimming pool so that the plate acquires birefringent properties by the tension effect. Therefore, this invention refers to a device for detecting accidental falls, whether sudden or slow, into swimming pools, specifically those of children.
The invention is characterized in that it is provided with devices sensitive to the level variation of a given value in the liquid mass of a swimming-pool, composed of a partially submerged device; the said device being provided with responsive means to said level variation in correspondence to a detecting device capable of generating a signal whose value corresponds to the detected body volume; the output of this detector being connected to a signal generating circuit which causes an alarm activation in response to the output signal of the detector. The invention comprises also other supplementary parts which will be further referred to in this description.